San Diego  A plan that would expand North County's Interstate 5 and coastal rail service won unanimous approval from the California Coastal Commission on Wednesday, giving the long-planned and controversial project one of its most important and final victories.

Called the North Coast Corridor program, the $6.5 billion package would add freeway, rail, bicycle, pedestrian and environmental improvements along a 27-mile stretch from La Jolla to Oceanside.

Spanning six cities and six lagoons, the public works project is considered one of the largest and most complex to date for the California Department of Transportation, the agency responsible for building it. Its most debated piece is a four-lane expansion of I-5.

“This is an opportunity to improve the quality of life for literally hundreds of thousands of residents and commuters,” said Mayor Kevin Faulconer, who was late for the meeting held at San Diego’s Catamaran Resort because of traffic. “We need this program. We need to get it across the finish line.”

In voting for the project, San Diego County Supervisor Greg Cox, a coastal commissioner, called scope of the project “mind-boggling” and a remarkable example of governments working together.

The project still faces hurdles.

Only a small fraction of the funding has been secured. And the freeway expansion piece is the subject of an ongoing lawsuit by critics who say coastal transit should be bolstered first, before any concrete is poured for freeway widening. No resolution is expected in that suit for some time, though it does not prevent officials from making final project plans or breaking ground.

With the state panel’s 'yes' vote, Caltrans expects to start freeway construction as early as next year, though it would take 30 to 40 years to complete all phases.

The new freeway lanes, called express lanes, would be added to the middle of the 5, eventually stretching the entire 27 miles and costing an estimated $3.5 billion. Like North County’s I-15 express lanes, they would be open to carpools, buses, motorcycles, select clean air vehicles and toll-paying solo drivers.

On the rail side, the project would fill in major gaps to create a second track from the Orange County line to downtown San Diego.

Caltrans has said the I-5 widening is necessary to handle surging traffic growth on the corridor, where forecasts have called for 300,000 vehicle trips on the freeway each weekday by 2030, up from the 200,000 trips it handles now.

I-5 expansion route

Source: Caltrans

Michelle Gilchrist • UT

Speaking after the hearing, Allan Kosup, the agency’s I-5 corridor director, said Caltrans has scaled back its traffic estimates somewhat but stressed that the region will still grow.

“San Diego is growing more slowly. But we’re going to get there eventually,” he said.

Kosup said much of North County’s I-5 is now expected to reach 300,000 weekday vehicle trips by 2035 or 2040, not 2030.

Project opponents said at Wednesday's hearing that Caltrans had used outdated and deeply flawed traffic projections to justify the interstate expansion.

In 2003, Caltrans predicted a nearly 30 percent growth in traffic on the highway by 2030. The San Diego Association of Governments, or SANDAG, produced a smaller growth forecast seven years later. It said traffic would increase by only 17 percent between 2010 and 2040, according to a statement by the Cleveland National Forest Foundation, the nonprofit suing Caltrans over the expansion.